Fall-protection apparatus with braking device comprising flexure-borne pawl

ABSTRACT

A fall-protection apparatus comprising a rotationally-activated braking device that comprises at least one flexure-borne pawl.

BACKGROUND

Fall-protection apparatus such as self-retracting lifelines have oftenfound use in applications such as building construction and the like.

SUMMARY

In broad summary, herein is disclosed a fall-protection apparatuscomprising a rotationally-activated braking device that comprises atleast one pawl that is a flexure-borne pawl. In various aspects, such aflexure-borne pawl may be a velocity-actuated pawl and/or it may be anacceleration-actuated pawl. These and other aspects will be apparentfrom the detailed description below. In no event, however, should thisbroad summary be construed to limit the claimable subject matter,whether such subject matter is presented in claims in the application asinitially filed or in claims that are amended or otherwise presented inprosecution.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an exemplary fall-protection apparatus.

FIG. 2 is a perspective partially-exploded view of various components ofan exemplary fall-protection apparatus.

FIG. 3 is an isolated perspective exploded view of particular componentsof an exemplary fall-protection apparatus.

FIG. 4 is a plan view of an exemplary arrangement of flexure-bornepawls.

FIG. 5 is a plan view of another exemplary arrangement of flexure-bornepawls.

FIG. 6 is a perspective view of another exemplary arrangement offlexure-borne pawls.

FIG. 7 is a plan view of the exemplary arrangement of pawls of FIG. 6 .

FIG. 8 is an isolated perspective view of various components of anotherexemplary fall-protection apparatus.

FIG. 9 is a partially exploded view of the components of FIG. 8 .

FIG. 10 is an exploded view of some components of FIG. 9 .

FIG. 11 is a plan view of another exemplary arrangement of flexure-bornepawls.

FIG. 12 is a plan view of another exemplary arrangement of flexure-bornepawls.

FIG. 13 is a perspective exploded view of an exemplary friction brake.

Like reference numbers in the various figures indicate like elements.Some elements may be present in identical or equivalent multiples; insuch cases only one or more representative elements may be designated bya reference number but it will be understood that such reference numbersapply to all such identical elements. Unless otherwise indicated, allfigures and drawings in this document are not to scale and are chosenfor the purpose of illustrating different embodiments of the invention.In particular the dimensions of the various components are depicted inillustrative terms only, and no relationship between the dimensions ofthe various components should be inferred from the drawings, unless soindicated. Although terms such as “first” and “second” may be used inthis disclosure, it should be understood that those terms are used intheir relative sense only unless otherwise noted.

Geometric descriptors are used herein, unless otherwise specified, withreference to a drum 80 and an associated pawl-support plate 40 of afall-protection apparatus as described in detail herein and as shown inFIG. 2 . The term “axially” refers to a direction at least generallyparallel to the axis of rotation of the drum, plate, and associatedcomponents (e.g. axis of rotation 81 as shown in FIGS. 2 and 8 ). Theterm “radial” and like terms refers to a direction generally parallel tothe radius and diameter of the drum and plate and generallyperpendicular to the axial direction. The terms circumferential,circumferentially, and like terms, refer to an arcuate direction thatexhibits a generally constant radius relative to the axis of rotation ofthe drum and associated components (for example, orbital pathway 25 asindicated on FIG. 4 , follows a circumferential path).

The direction of rotation of various components (e.g. drum 80,pawl-support plate 40, and other items) in the instance that drum 80turns rapidly in the event of a user fall, is denoted in various FIGS.herein by an arcuate arrow labeled w. (Discussions herein will make itclear that these items can sometimes rotate in the opposite direction;however, the particular direction of fall-induced rotation will be usedin order to standardize terms used herein). Terms such as “leading” and“trailing” are used to characterize the relative position of variousitems that can travel along a generally circumferential pathway in theevent of the above-described rotation. “Leading” refers to a componentthat, upon such rotation, passes a fixed point before a “trailing”component passes the fixed point. In other words, end 22 of pawl 20 asshown in FIG. 4 , is a leading end; end 23 is a trailing end of pawl 20.(In some instances, a “leading” direction and a “trailing” direction maybe respectively referred to herein as a circumferentially-forwarddirection and a circumferentially-rearward direction.) The meanings ofall of these terms, and related terms and phrases, will be readilyapparent based on the descriptions and Figures presented herein.

As used herein as a modifier to a property or attribute, the term“generally”, unless otherwise specifically defined, means that theproperty or attribute would be readily recognizable by a person ofordinary skill but without requiring a high degree of approximation(e.g., within +/−20% for quantifiable properties). The term“substantially”, unless otherwise specifically defined, means to a highdegree of approximation (e.g., within +/−10% for quantifiableproperties). The term “essentially” means to a very high degree ofapproximation (e.g., within plus or minus 2% for quantifiableproperties; it will be understood that the phrase “at least essentially”subsumes the specific case of an “exact” match. However, even an “exact”match, or any other characterization using terms such as e.g. same,equal, identical, uniform, constant, and the like, will be understood tobe within the usual tolerances or measuring error applicable to theparticular circumstance rather than requiring absolute precision or aperfect match. The term “configured to” and like terms is at least asrestrictive as the term “adapted to”, and requires actual designintention to perform the specified function rather than mere physicalcapability of performing such a function. All references herein tonumerical parameters (dimensions, ratios, and so on) are understood tobe calculable (unless otherwise noted) by the use of average valuesderived from a number of measurements of the parameter.

DETAILED DESCRIPTION

Disclosed herein is a fall-protection apparatus, by which is meant anapparatus that acts to controllably decelerate a human user of theapparatus in the event of a user fall. By definition, such afall-protection apparatus is a non-motorized apparatus. By this is meantthat a safety line of the apparatus is not moved (i.e., extended orretracted from a housing of the apparatus) by way of an electricallypowered motor; in other words, the apparatus is not used as part of asystem (e.g., an elevator, a hoist, etc.) that uses one or more motorsto raise or lower a load.

In many embodiments, such a fall-protection apparatus may be aself-retracting lifeline (SRL); i.e., a deceleration apparatuscomprising a housing at least partially contains a drum-wound safetyline that can be extended from the housing and retracted into thehousing under slight tension during normal movement of a human user ofthe apparatus, and which, upon the onset of a user fall, automaticallyarrests (i.e., slows to a controlled rate, or completely stops) the fallof the user. Such an apparatus may comprise a safety line (made e.g. ofmetal or any other suitable material) that can be extended out of alower end of the apparatus with the apparatus having an upper, anchorageend which may be connected e.g. to a secure anchorage of a workplace.Often, such an apparatus may comprise a drum that is rotatably mountedwithin a housing therein such that such that the safety line can bewound about the drum when the line is retracted into the housing. Suchan apparatus will further comprise a rotationally-activated brakingdevice. By this is meant a device that is configured to slow (e.g. stop)the rotation of the drum upon rotation of the drum with a velocityand/or acceleration or combination thereof, that is above apredetermined threshold value.

An exemplary fall-protection apparatus (a self-retracting lifeline) 1 isdepicted in FIG. 1 . Such an apparatus may comprise a housing 111 thatis provided e.g. from a first housing piece 112 and second housing piece113 that are assembled and fastened together to form the housing.Housing pieces 112 and 113 may be fastened together e.g. by bolts or byany other suitable fasteners. Various ancillary components such as e.g.one or more nuts, bolts, screws, shafts, washers, bushings, gaskets,bearings, labels, auxiliary housing pieces or shields, and the like, areomitted from the Figures herein for ease of presentation of componentsof primary interest; ordinary artisans will readily appreciate that anysuch items may be present as needed for the functioning of apparatus 1.In some embodiments, housing 111 may be load-bearing; in someembodiments, a load bracket or similar component may be present and mayprovide at least a portion of the load-bearing path of the apparatus.

Further details of exemplary apparatus 1 are depicted in FIG. 2 , whichis a partially exploded view with the second housing piece 113 omitted.Within an interior space at least partially defined by housing 111 is adrum 80, which defines a receiving space 88 (indicated in FIG. 8 ) intowhich is wound (e.g., spiral-wound) a length of safety line 115 (withthe term line broadly encompassing any elongate, windable load-bearingmember, including e.g. webbing, cable, rope, etc., made of any suitablesynthetic or natural polymeric material, metal, etc., or any combinationthereof). A proximal end of line 115 is connected, directly orindirectly, to drum 80 (such a connection encompasses configurations inwhich the proximal end of line 115 is connected to a shaft 82 on whichdrum 80 is mounted). Drum 80 is rotatably mounted within housing 111,e.g. by being rotatably mounted on a shaft 82 and/or by being mounted ona shaft 82 that is rotatable relative to the housing. A biasing member86 (not visible in FIG. 2 but indicated in generic representation inFIG. 1 , and which may be e.g. a suitable spring such as a spiral-coiledtorsion spring) may be provided, which serves to bias the drum towardrotating in a direction that will retract safety line 115 onto the drumunless the biasing force is overcome e.g. by movement of a human user.

Apparatus 1 comprises a rotationally-activated braking device 10, asshown in exemplary embodiment in FIG. 2 . Such a rotationally-activatedbraking device relies on one or more pawls 20. Typically, the at leastone pawl 20 is co-rotatable with drum 80. By this is meant that thepawls are able to rotate along with drum 80, with the pawl(s) moving inan orbital path about a center of orbital motion that coincides with theaxis of rotation of the drum. In various exemplary arrangementsillustrated in the Figures herein, such an arrangement is achieved bymounting pawl(s) 20 on a pawl-support plate 40 which is mounted on thesame shaft 82 on which drum 80 is mounted. In other words, in at leastsome embodiments pawl-support plate 40 may be axially co-mounted withdrum 80 and may be co-rotatable with drum 80. In some embodiments such apawl-support plate may be fixed to (e.g. attached directly to) drum 80.In some embodiments, such an arrangement may be achieved e.g. bymounting pawl(s) directly on drum 80, e.g. so that a side flange or wallof drum 80 serves as a pawl-support plate. In such embodiments,pawl-support plate 40 will be in fixed relation with (i.e., will alwaysrotate in unison with) drum 80. In some embodiments as discussed laterherein, plate 40 will be configured so that it can rotate slightlyrelative to drum 80 under some circumstances (e.g. upon exposure tosufficient acceleration in the event of a user fall). However, even insuch embodiments, plate 40 will typically rotate in unison with drum 80the vast majority of the time during ordinary use of apparatus 1.

The one or more pawls 20 are arranged (e.g. mounted on a pawl-supportplate 40 as described in detail later herein) so that they can bodilymove between a disengaged position and an engaged position. The pawl(s)20 are configured so that in ordinary use of the fall-protectionapparatus, an engaging end 22 of a pawl 20 is maintained in anon-engaged position in which it does not engage with any component(e.g. a ratchet tooth) that would limit the rotation of the drum. Thisarrangement allows the drum to rotate freely back and forth thusallowing extension and retraction of the safety line in response tomovements of a human user of the fall-protection apparatus as the usergoes about their workplace activities. In the event that the drum beginsto rotate (in direction ω as indicated e.g. in FIG. 4 ) above apredetermined threshold value of velocity (and/or, in some cases,acceleration, as discussed in detail later herein), at least one pawl ismotivated into an engaged position in which the engaging end 22 of thepawl 20 is able to physically contact a tooth of a ratchet to slow orstop the rotation of the drum. Exemplary ratchets 90 and teeth 91thereof are depicted in exemplary embodiments in various Figures herein;however, it will be appreciated that many ratchet arrangements arepossible, as is discussed in detail later herein. Strictly speaking, apawl will not “engage” with a ratchet tooth until its engaging endactually contacts the tooth. However, for purposes of description, apawl will be considered to be in an engaged position upon the pawlhaving been actuated so that its engaging end is in a position (e.g.having moved radially outward) in which it will contact a ratchet toothupon continued motion of the pawl along its orbital path.

In various Figures herein, some pawls are depicted in an engagedposition while others are depicted in a disengaged position. Forclarity, in certain Figures herein a pawl that is in an engaged positionis subscripted “e” (e.g. 20 e). It will be appreciated that when theapparatus is in a non-fall situation (e.g. with the drum rotating veryslowly or not at all), all such pawls will typically be in a disengagedposition (e.g. a “home” position as described later herein).

In use of a rotationally-activated braking device as disclosed herein,engaging of at least one pawl with a tooth of a ratchet will at leastslow, e.g. will arrest, the rotation of the drum. With some such brakingdevices, the rotationally-activated braking device may bring the drum toa “hard stop” in which the rotation of the drum ceases essentially atthe instant that the pawl engages the tooth. In many such cases, thesafety line of such an apparatus may include a so-called shock absorber(e.g. a tear web or tear strip) to minimize the force experienced by ahuman user as the user is brought to a halt. (It will be understood thatthe term “hard stop” is used for convenience in distinguishing such astop from a more gradual stop that relies on the use of a friction brakeas described later herein; the term “hard stop” does not imply that theuser is subjected to, e.g., excessively hard forces in being brought toa halt.) With some other such braking devices (e.g. as depicted invarious Figures herein), the rotationally-activated braking devicerelies on a friction brake that, rather than bringing the drumnear-instantly to a “hard stop”, brings the drum to a halt in a moregradual manner as described in detail later herein. This can minimizethe force experienced by a human user as a fall is being arrested, e.g.without requiring the presence of a shock absorber in the safety line.

In use of exemplary fall-protection apparatus 1, an upper, anchorage end108 of the apparatus may be connected (e.g. by way of connection feature114) to a secure anchorage (fixed point) of a workplace structure (e.g.,a girder, beam or the like). The distal end of line 115 may then beattached (e.g., by way of hook 116) to a harness worn by a worker. Asthe human user moves away from the fixed anchorage, drum 80 rotates in afirst direction (w) so that line 115 is extended (paid out) from withinhousing 111. As the user moves toward the fixed anchorage, drum 80rotates in a second, opposite direction (e.g. under the urging of atorsion spring or other biasing member), so that line 115 isautomatically self-retracted within housing 111 and wound upon drum 80.During such user activities, pawl(s) 20 is maintained in a disengagedposition in which an engaging end 22 of pawl 20 does not engage a tooth91 of a ratchet 90 of the rotationally-activated braking device. In theevent that the human user falls and causes line 115 to begin rapidlyextending from housing 111 and drum 80 to rotate rapidly in direction w,a leading/engaging end 22 of pawl 20 is caused to move to a position inwhich it can engage with a ratchet tooth 91 of a ratchet 90 (i.e., isactuated) by the arrangements disclosed herein, whereupon the falling ofthe worker is arrested as discussed in detail herein.

As disclosed herein, a fall-protection apparatus 1 comprises at leastone flexure-borne pawl 20. In many embodiments, multiple suchflexure-borne pawls 20 may be present and may be supported by a commonpawl-support plate 40, as discussed later herein (noting that in someembodiments a sidewall or flange of drum 80 may serve as a pawl-supportplate rather than a separate pawl-support plate 40 being used in themanner of FIG. 2 ). In some embodiments, three such flexure-borne pawls20 may be provided, as shown in exemplary embodiment in FIGS. 2-5herein. Such pawls may be e.g. circumferentially spaced along a circularpath (when viewed along the axis of rotation 81 of drum 80, pawl-supportplate 40, etc.) around a pawl-support plate 40 in the general mannershown in FIGS. 2-5 .

As is evident from the plan view (looking along axis of rotation 81) ofFIG. 4 , the at least one pawl is configured so that upon rotation ofpawl-support plate 40 around its axis of rotation 81, pawl(s) 20 willfollow a generally circular orbital path 25 around axis of rotation 81.When drum 80 and pawl-support plate 40 are rotating at a rotationalvelocity ω below a predetermined threshold value, all such pawls 20 willbe in a first, disengaged position. A pawl 20 will be actuated (i.e.,caused to move from a first, disengaged position, toward and into asecond, engaged position) when the velocity of the pawl 20 along itsorbital path exceeds the predetermined threshold value. In someembodiments, a pawl 20 will not be not significantly affected (e.g.actuated) by any acceleration that the pawl may be experiencing, whilein other embodiments such a pawl may be actuated by acceleration (and/orthe velocity-actuation of the pawl may be modulated by theacceleration), as discussed in detail later herein.

Flexure-Borne Pawl

By a flexure-borne pawl is meant a pawl 20 that is attached to a flexurearm 30. Specifically, a trailing end 23 of pawl 20 will be attached to aleading end 31 of a flexure arm 30. Trailing end 32 of flexure arm 30will be attached to a flexure arm anchor 50 as shown e.g. in FIG. 3 . Aflexure arm 30 thus extends from flexure arm anchor 50 to pawl 20, andis elongate along this extent. The path of a flexure arm, from anchor 50to pawl 20, will often be at least generally circumferential, and mayalso extend at least generally radially outward, as will be evident fromvarious exemplary arrangements presented in the Figures herein. Often, aflexure arm 30 or set of flexure arms 30 may exhibit a somewhat spiralappearance as evident in several Figures herein. A flexure arm 30 istypically sheetlike or rodlike over much of its elongate length, e.g. soas to exhibit a thickness “t” (as indicated in FIG. 4 ) that isrelatively small (e.g. by a factor of at least 10) in comparison to theoverall elongate length of the flexure arm. Flexure arm 30 is configuredto deflect (e.g. bend) at least slightly, in a direction that is atleast generally radially outward, to allow pawl 20 to move generallyradially outward under the influence of centrifugal force as discussedbelow. It will be understood that this deflection will take the form ofreversible deformation that remains within the elastic limit of thematerial of which the flexure arm is made. It will further beappreciated that this deflection is an extremely low-friction process,the advantages of which are discussed later herein.

A flexure arm anchor 50 from which a flexure arm 30 extends is typicallypositioned axially adjacent to pawl-support plate 40, e.g. protrudingaxially away from pawl-support plate 40 (such terminology does not implythat such an anchor 50 must necessarily be an integral portion of plate40, although in some embodiments it may be). In at least someembodiments, a flexure arm anchor 50 will be fixed in position relativeto pawl-support plate 40; e.g., the anchor 50 may be non-movablyattached to plate 40. In some embodiments, multiple individual pawls 20may be respectively connected to multiple individual anchors 50 (e.g. inthe form of individual posts). In some embodiments, some or all flexurearm anchors 50 may be integral portions of a pawl-support module 51 asseen most easily in FIG. 3 . In some embodiments multiple flexure armanchors 50 may be circumferentially spaced along the perimeter of asingle (e.g. integral) pawl-support module 51, e.g. as in FIGS. 4-5herein.

In some embodiments a pawl 20 and a flexure arm 30 may be madeseparately and then attached to each other (e.g. as in the design ofFIG. 10 , discussed later herein). In other embodiments, a pawl andflexure arm may be attached to each other by way of being integral witheach other, e.g. as in the design of FIG. 3 . Here and elsewhere herein,the term “integral” and like terminology denotes items that are made ina single, common operation (e.g. by molding), as portions of a singleunitary component. (By definition, items that are made separately andsubsequently joined together are not integral as defined herein.)Similarly, in some embodiments a flexure arm 30 may be made separatelyfrom a flexure arm anchor 50 and then subsequently attached thereto. Inother embodiments a flexure arm 30 and a flexure arm anchor 50 may beintegral. In some embodiments, a pawl, a flexure arm, and a flexure armanchor 50 may all be integral with each other. For example, pawls andflexure arms may all be integrally connected to a single pawl-supportmodule 51 as noted above and as illustrated in FIG. 3 .

As is evident from FIG. 3 , in some embodiments such a pawl-supportmodule 51 may be separately made from pawl-support plate 40 and may beattached to plate 40 e.g. by way of fasteners 45 that reside in orifices47 of pawl-support plate 40 and orifices 53 of pawl-support module 51 asshown in FIG. 3 . In some embodiments, a pawl-support module 51 (andpossibly flexure arms 30) may be integral with pawl-support plate 40rather than being made separately and then attached thereto. Whateverthe particular design, in many embodiments a pawl-support module 51 willbe fixed (not rotatable) relative to pawl-support plate 40. The abovediscussions make it clear that the term flexure arm anchor as usedherein, does not require that an anchor must be e.g. a free-standingpost; rather, a flexure arm anchor may simply be a local portion of apawl-support module 51 from which a flexure arm extends.

The functioning of a flexure-borne pawl 20 may be appreciated based onFIGS. 4 and 5 , which are plan views looking along axis of rotation 81.(These are conceptual views with various items omitted so that certainitems and their function can be highlighted.) Pawls 20 and flexure arms30 are configured so that when drum 80 (not shown in FIGS. 4 and 5 ),pawl-support plate 40, and pawls 20, are not rotating (or are rotatingslowly), pawls 20 will remain in a disengaged position as shown in FIG.4 . Upon rotation of the drum, pawl-support plate 40, and pawls 20 abovea predetermined threshold value of rotational velocity a), at least oneof the pawls will be urged by centrifugal force, generally radiallyoutward as indicated by block arrow 28 of FIG. 4 . This centrifugalforce will be high enough to overcome the resistance of flexure arm 30to bending, thus flexure arm 30 will deflect slightly to allow thismotion. This will place pawl 20 in an engaged position in which anengaging end 22 of the flexure-borne pawl 20 can contact a tooth 91 ofthe ratchet 90 as illustrated by the particular pawl denoted 20 e inFIG. 5 . (The other two pawls in FIG. 5 are shown as having movedradially outward to an engaged position but have not actually contacteda ratchet tooth.)

Bodily Movement of Pawl

By definition, a flexure-borne pawl 20 as disclosed herein will movegenerally radially outward from the disengaged position toward and intothe engaged position, in a bodily manner. By moving “bodily” is meantthat the pawl moves generally radially outward as a whole, in itsentirety. That is, while in some instances the “leading” end 22 of apawl 20 may move further radially outward than the “trailing” end 23 ofthe pawl 20, no portion of the pawl will move radially inward ratherthan outward. A flexure-borne pawl is thus distinguished from, forexample, a conventional pivot-mounted pawl that comprises a pivot pointthat is located within the perimeter of the pawl. Such a pivot-mountedpawl is actuated by way of an engaging end of the pawl moving radiallyoutward, and an opposite end of the pawl moving in the oppositedirection, radially inward. (Some pivot-mounted pawls work in reversefashion to this; however, such a pawl still has a portion that movesinward, and a portion that moves outward). In many embodiments, the onlytype of pawls that will be present in an arrangement as disclosed hereinwill be flexure-borne pawls, e.g. no pivot-mounted pawl or pawls will bepresent.

The use of flexure-borne pawls can advantageously minimize the amount offriction that arises in operation of the pawls. That is, a pivotalconnection by which a pivot-mounted pawl is mounted to e.g. a post of apawl-support plate, may exhibit friction due to the sliding of onesurface against another as the pawl pivots. This friction may vary basede.g. on manufacturing tolerances, the presence of even small amounts ofdebris into the pivotal connection, and so on. In contrast, a pawl thatis moved purely by the flexing of a flexure arm does not involve slidingof one surface against another to any significant extent. (Inparticular, in many embodiments pawls 20 and flexure arms 30 will bepositioned so that they do not contact major surface 41 of pawl-supportplate 40 to an extent that gives rise to significant frictionalinteraction.) The use of flexure-borne pawls can thus enhance theperformance of a rotationally-activated braking device e.g. byminimizing variability in operating performance due to friction. It willalso be appreciated that the use of flexure-borne pawls may offeradvantages e.g. in terms of fewer parts being needed, and/or in allowingthe use of a simplified manufacturing process.

Ordinary artisans will appreciate that a flexure-borne pawl differs froma conventional pivot-mounted pawl in another aspect. Typically, apivot-mounted pawl is biased by way of a biasing member (e.g. a spring)that serves to urge the pawl in a particular direction, which istypically limited by a physical stop. Thus, the biasing member (e.g.spring) of a pivot-mounted pawl typically experiences at least someminimal force (e.g. tension) even when the apparatus is not being used.In contrast, in some embodiments, when apparatus 1 is not being used, aflexure-borne pawl may be in a disengaged position that is a “home”position (i.e., a “neutral” position that the pawl will inherentlyassume when the drum is not rotating, or is rotating very slowly). Insuch a home position, the flexure arm 30 will not be experiencing anyforce that urges it radially inward or outward (in some instances, theonly force that is operating may be gravity). It is only when (uponsufficient rotation of the drum) the pawl is urged radially outward bycentrifugal force, that the flexure arm becomes flexed and thus developsa restoring force that acts as a biasing force that opposes the tendencyof the pawl to move further outward. Thus, a flexure arm configured inthis manner may not be subject to a near-continuous force in the mannerof a conventional spring of a conventional pivot-mounted pawl. However,if desired, in some embodiments a physical stop may be provided that,for example, may prevent the flexure arm from e.g. moving too farradially inward in the event that the apparatus is jostled or dropped.In some embodiments, such a physical stop may be positioned so that itcauses the flexure arm to reside at least slightly away from (e.g.radially outward of) what would otherwise be its natural, “home”position.

Based on the disclosures herein, ordinary artisans will appreciate thatvarious design parameters (e.g. the size, shape, mass, massdistribution, etc. of the pawls; and/or, the length, shape, thickness,and, in particular, the flexural modulus and bending stiffness, of theflexure arm) may be chosen in combination to provide that the pawl isactuated from a disengaged position to an engaged position at apredetermined threshold of rotational velocity.

One design parameter is the number of flexure-borne pawls that arepresent. In some embodiments, a single pawl may be used. In otherembodiments, three pawls may be used, e.g. as in the exemplaryarrangements of FIGS. 2-5 . FIGS. 6 and 7 illustrate an exemplary designin which two pawls are used (in these Figures, the various componentsuse the same numbering as for corresponding components in FIGS. 2-5 ).Any greater number of pawls (e.g. four pawls), may be used if desired.In embodiments in which pawls are provided in pairs (e.g. one pair ofpawls, or two pairs for four pawls total) the pawls 20 of any such pairmay be located in circumferentially-opposing positions from each other(i.e., on opposite sides of the axis of rotation 81 of drum 80 andpawl-support plate 40, when viewed along axis of rotation 81). A pair ofsuch oppositely-located flexure-borne pawls is depicted in exemplaryembodiment in FIGS. 6 and 7 . Each such pawl comprises a leading end 22and a trailing end 23, and is attached to a leading end 31 of a flexurearm 30. The trailing end 32 of each flexure arm is attached to a flexurearm anchor 50; each such flexure arm anchor 50 is an integral componentof a pawl-support module 51. In the exemplary arrangement of FIGS. 6 and7 , pawls 20, flexure arms 30, and flexure arm anchors 50, are allintegral with a single, integral pawl-support module 51.

Comparison of FIGS. 4-5 and 7 reveal another useful design parameter,which is the amount of circumferential “wrap” exhibited by thecombination of a pawl 20 and the flexure arm 30 that bears the pawl.Such wrap may be characterized by the angle between two lines—one drawnfrom axis of rotation 81 to the tip of leading end 22 of pawl 20, theother drawn from axis of rotation 81 to the location at which thetrailing end 32 of flexure arm 30 meets flexure arm anchor 50. Invarious embodiments, any particular pawl and its associated flexure armmay exhibit a wrap of at least 30, 45, 60, 90, 120, 150, or 180 degrees.In further embodiments, a pawl/flexure arm may exhibit a wrap of no morethan 260, 200, 165, 135, 100, or 70 degrees. (In general, the greaterthe degree of “wrap”, the more a set of pawls and flexure arms mayexhibit a shape that resembles a spiral.) By way of specific examples,the exemplary pawls/flexure arms of FIG. 4 exhibit a circumferentialwrap in the range of approximately 75 degrees; the exemplarypawls/flexure arms of FIG. 7 exhibit a circumferential wrap in the rangeof approximately 155 degrees. The design shown in FIG. 11 (whichincludes three flexure-borne pawls and which will be discussed in detaillater herein) exhibits a circumferential wrap in the range ofapproximately 200-210 degrees. It will be appreciated that the use of alarge amount of circumferential wrap can allow a flexure arm to berelatively long and thus can allow a desired flexibility of the flexurearm to be achieved without, for example, requiring the flexure arm tohave an extremely small thickness.

Various Figures herein (e.g. FIGS. 4, 5, 7 , and the later-discussedFIGS. 11 and 12 ) depict an arrangement in which flexure arms areforwardly wrapped. By this is meant that the flexure arms extend fromtheir respective anchors to their junction with the pawls, in adirection that coincides with the above-described rotation direction(i.e., the direction of fall-induced rotation), as evident e.g. fromFIG. 4 . In such an arrangement, the flexure arms are thus “pushing” thepawls in the rotation direction as the drum rotates. However, in someembodiments this can be reversed, so that the flexure arms extend fromtheir anchors to their junction with the pawls, in a direction that isopposite the rotation direction. This will be referred to as aconfiguration in which the flexure arms are rearwardly wrapped; in suchan arrangement, the flexure arms will be “pulling” the pawls in therotation direction as the drum rotates. In such a design, the end ofeach pawl at which the flexure arm approaches the pawl will be theleading end of the pawl, and will be the engaging end that engages witha ratchet tooth. The opposing end of the pawl will be the trailing end.

Inspection of FIGS. 4, 7 and 11 reveals additional useful designparameters. For example, in various embodiments the long axis of atleast a portion of a flexure arm 30 may have a selected orientation inrelation to the orbital path (e.g. orbital path 25 as denoted in FIG. 4) followed by the pawl 20 that is borne by that flexure arm. Thus invarious embodiments, a long axis of a flexure arm 30 may be locallyaligned with an orbital path to within a desired local alignment angle,along a chosen percentage of the elongate extent of the flexure arm. Forexample, inspection of FIG. 7 reveals that in this design, substantiallythe entire length of each flexure arm 30 is locally aligned (e.g. so asto exhibit a local alignment angle of less than plus or minus 5 degrees,e.g. of 0 degrees) with an orbital path that will be traced out by pawls20, upon rotation of the drum with which this set of pawls is used.Inspection of FIG. 4 reveals that in this design, substantially theentire length of these flexure arms 30 is locally aligned withinapproximately 30 degrees of the orbital path that will be traced out bypawls 20. It is evident that in the design of FIG. 4 , the localalignment is not as constant along the length of flexure arm 30 as it isin the design of FIG. 7 ; that is, in FIG. 4 the local alignment appearsto vary from 0 degrees (exactly locally parallel, at certain locations)to approximately 30 degrees. Although it differs in other respects fromthe design of FIG. 4 , the design of FIG. 11 similarly appears toexhibit a local alignment angle that varies, over the length of flexurearm 30, from 0 degrees to approximately 30 degrees.

In various embodiments a flexure arm may exhibit a local alignmentangle, over any specified extent of the elongate length of a flexurearm, of e.g. less than plus or minus 70, 50, 40, 30, 20, 10, or 5degrees. In further embodiments, any of these conditions may hold overat least 20, 40, 60, 80, 90, 95, or essentially 100% of the elongatelength of the flexure arm. The measurement of such a local alignmentangle, at any location along the elongate length of a flexure arm, canbe performed as follows. At the desired point on the flexure arm, afirst line is drawn that coincides with the long axis of the flexure armat least at that point (if the flexure arm is arcuate at that point, aline is drawn that is tangent to the flexure arm at that point). Asecond line is drawn from axis of rotation 81, radially outward throughthat point. The second line is continued radially outward until itintersects the orbital path traced out by the pawl borne by that flexurearm. A tangent to the orbital path is drawn at this point ofintersection, which provides a third line. The angle between the thirdline and the first line provides the above-enumerated local alignmentangle.

Inspection of FIGS. 4, 7 and 11 reveal further variations that can beaccommodated or advantageously used. For example, in some embodiments aflexure arm 30 may be relatively straight along its entire length, as inthe design of FIG. 4 . In some embodiments a flexure arm 30 may be atleast generally uniformly arcuate (i.e. with a local radius of curvaturethat does not vary by more than e.g. 20, 10, 5, or 2%) along the entirelength of the flexure arm, as in the design of FIG. 7 . In someembodiments, a flexure arm may comprise a leading segment 33 and atrailing segment 38 that are connected by an elbow 34, as in the designof FIG. 11 . In some such embodiments, segments 33 and 38 may berelatively straight, with elbow 34 being more arcuate, also as evidentin FIG. 11 . These various exemplary designs make it clear that aflexure arm 30 may vary from being e.g. uniformly arcuate along most orall of its elongate length, to comprising any number of relativelystraight segments interspersed with any desired number of e.g. sharplycurved segments.

In some embodiments, the thinnest dimension of the flexure arm (e.g.thickness “t” as denoted in FIG. 4 ) may be oriented in a generallyradially inward-outward direction, along at least a portion of theelongate length of the flexure arm. In other words, at any particularpoint along the elongate length of the flexure arm, the thickness “t” ofthe arm at that point may be at least generally aligned with a line thatis drawn from axis of rotation 81 through that point. In variousembodiments, the thickness “t” may be aligned within plus or minus 50,30, 20, 10, or 5 degrees of radially inward-outward, e.g. along at least20, 40, 60, 80, 90, or 95% of the elongate length of the flexure arm.

Various figures herein depict exemplary arrangements in which arelatively sharp demarcation is present between a pawl 20 and a flexurearm 30 to which the pawl is attached. However, this is not necessarilyrequired. For example, a flexure arm could gradually increase inthickness (whether smoothly or stepwise) from its trailing end to itsleading end, with a leading portion of the flexure arm beingsufficiently thick (and e.g. massive) to serve as a pawl. All suchdesigns fall within the overall concept of a flexure-borne pawl and aflexure arm to which such a pawl is attached. Furthermore, although theFigures herein depict flexure arms that are relatively uniform inthickness, and uniform in width (in the axial direction), this does notnecessarily have to be the case. Although the Figures herein depictflexure arms that are in the form of a single, uninterrupted piece, thisdoes not necessarily have to be the case. For example, in someembodiments a flexure arm could comprise an elongate slot that extendsalong the long axis of at least a portion of the flexure arm; in fact,in some embodiments a pawl could be connected to a flexure anchor by wayof two (or more) elongate flexure arms that are separate from each otheralong a portion, or the entirety, of their length.

Still further, the concept of a pawl that is “attached” to a flexure armdoes not necessarily require that the pawl must be permanently attached,e.g. adhesively bonded or welded, to the flexure arm. Rather, in someembodiments a pawl may e.g. comprise a slot and a seating cavityconfigured to respectively accept a leading portion of the flexure armand an enlarged seating head at the terminal end of the flexure arm. Theenlarged seating head and leading portion of the flexure arm may beinserted into these openings e.g. as shown in FIG. 11 to attach the pawlto the flexure arm. Arrangements of this general type fall within theoverall concept of a pawl that is attached to a flexure arm.

Any of the above-described components may be made of any suitablematerial. In particular, the flexure arms may be made of a material witha suitable flexural modulus (and with properties that will be maintainedover aging). In many embodiments, the flexure arms may be made of asuitable metal, e.g. stainless steel. In some embodiments, the flexurearms may be made of a suitable engineering plastic, e.g. polyether etherketone (PEEK), acrylonitrile-butadiene-styrene (ABS) polymers,carbon-fiber reinforced polymers (of any suitable polymericcomposition), and so on. In some convenient embodiments, the flexurearms may be made by injection molding of any such material. In someembodiments flexure arms, pawls that are attachable to flexure arms; or,a pawl-support module that integrally includes flexure arm anchors,flexure arms, and, in some embodiments, the pawls themselves, may bemade of injection-molded metal.

In some particular embodiments, flexure arms and/or pawls that areattachable to flexure arms; or, a pawl-support module that integrallyincludes flexure arm anchors, flexure arms, and, in some embodiments,the pawls themselves, may be made of an amorphous metal. By an amorphousmetal is meant a metal or metal alloy (most such materials are in factalloys) that exhibits a disordered, i.e. non-crystalline, atomic-scalestructure that is characterized by a near-complete absence of grainboundaries. (Such materials are sometimes referred to as bulk metallicglasses.) In many embodiments, such a material may be molded to form aflexure arm or even to form an entire pawl-support module and integralflexure arms (and optionally, pawls) thereof. Such materials may haveunique properties (e.g., a combination of flexural modulus, yieldstrength, and durability) that render them highly useful to serve asflexure arms for the uses herein. Such materials may be made of anysuitable alloy (e.g. a zirconium-based alloy) and may be formed into thedesired items by any suitable method, e.g. by injection molding

Buttress

The above discussions make it clear that it is advantageous to selectthe properties (e.g. flexural modulus and bending stiffness, yieldstrength, and so on) of a flexure arm 30 in view of the desiredrelationship between the centrifugal force exerted on the flexure arm asa result of rotation, and the resulting amount of radially outwarddisplacement of the pawl. To provide the most unrestricted design spacewithin which to operate in regard to the flexure arm, arrangements canbe made that relieve other design constraints that might otherwise bepresent.

For example, in some embodiments a pawl-support plate 40 may comprise atleast one buttress 60 that protrudes axially from the pawl-support plate(e.g. from major surface 41 of plate 40, on the same side of the platethat the pawls and flexure arms are present), as shown in exemplaryembodiment in FIG. 3 . In some embodiments, such a buttress 60 can be anintegral part of pawl-support plate 40; in other embodiments, such abuttress may be made separately and then attached to plate 40. Such abuttress 60 can be positioned so that at least a portion of the buttress60 is positioned circumferentially rearward of at least a portion of thetrailing end 23 of pawl 20, as shown in exemplary embodiment in FIG. 4 .(Often, at least a portion of the buttress may be positioned at leastgenerally radially outward of at least a portion of pawl 20, also asevident in FIG. 4 ).

A buttress 60 will comprise a contact surface 61 (indicated in FIGS. 3and 4 ) that is configured to be contacted by a portion of trailing end23 of pawl 20 under certain conditions, as explained below. Typically,pawl 20 and buttress 60 are configured so that a circumferential gap 52(which may be relatively small, as evident in FIG. 4 ) is presentbetween contact surface 61 of buttress 60, and trailing end 23 of pawl20, e.g. at their point of closest approach. Gap 52 will typically bepresent when the pawl is in a disengaged position (in other words,during ordinary use of apparatus 1, no portion of pawl 20 will typicallybe in contact with any portion of buttress 60). Such a gap 52 may bepresent momentarily after pawl 20 has moved radially outward into anengaged position, before being eliminated as described below.

In a braking (e.g. fall-arrest) operation, a pawl 20 will move generallyradially outward so that a leading end 22 of the pawl engages with atooth 91 of a ratchet 90, as described earlier herein and as shown inFIG. 5 . This will bring pawl 20 to a sudden stop and will developconsiderable force on the pawl 20, acting in a generallycircumferentially-rearward direction as indicated by block arrow 29 inFIG. 5 . This force will urge pawl 20 slightly circumferentiallyrearward far enough to close gap 52 and thus to cause at least a portionof trailing end 23 of pawl 20 to come into contact with the contactsurface 61 of buttress 60. In other words, engaging of the leading endof the pawl with the ratchet can cause the trailing end of the pawl tobe “jammed” into the leading end of the buttress.

Buttress 60 can be configured to be extremely strong (e.g. in comparisonto flexure arm 30). Buttress 60 can thus bear, and dissipate, at least aportion of the force that is developed on the pawl upon the engaging ofthe pawl with the tooth of the ratchet. In various embodiments, thebuttress may bear and dissipate a significant amount of this force (e.g.60, 80, 90, 95, 98, or essentially 100% of the force).

Any number of buttresses may be used, e.g. one, two, three, four ormore. In some embodiments, the number of buttresses may equal the numberof pawls (e.g., three and three as in the design of FIG. 2 ). In manysuch embodiments, each buttress may be positioned in relation to aparticular pawl so that upon engaging of the pawl with a ratchet tooth,the pawl will be jammed against that particular buttress.

It will be appreciated that the providing of a buttress in this mannercan substantially eliminate any need to strengthen flexure arm 30 to beable to bear the full amount, or even a significant portion, of theforce that develops when the pawl engages a ratchet tooth. This allowsthe flexure arm to be designed (e.g. with a relatively small thickness“t”) to allow the arm to exhibit flexibility commensurate with a desiredforce-displacement relationship. Otherwise, a flexure arm that isoptimized to provide the desired flexibility might, for example,irreversibly deform (e.g. buckle or accordionize) under the large forcethat develops when the pawl engages a ratchet tooth in the course ofarresting a fall. Thus according to the present arrangements, in afall-arrest event, a pawl 20 may be urged slightly circumferentiallyrearward in such manner as to e.g. momentarily slightly deflect itsflexure arm 30; however, such deflection will be below the elastic limitof the flexure arm and will be reversible.

The above discussions have concerned the use of a buttress with aforwardly-wrapped configuration of flexure arms and pawls as defined anddescribed previously herein. In some embodiments, a rearwardly-wrappedconfiguration of flexure arms and pawls may be used. In such cases, anysuch buttress(es) can be used and can still be configured so that theengaging of the leading end of a pawl with a ratchet will cause thetrailing end of the pawl to be “jammed” into the leading end of thebuttress. The primary difference will be that in this case the trailingend of the pawl will be the end that is generally opposite the end fromwhich the flexure arm approaches the pawl.

In some embodiments, the trailing end 23 of pawl 20, and contact surface61 of buttress 60, may exhibit complementary shapes to ensure thattrailing end 23 is guided into a desired contact position with buttress60. Any such design should also ensure that the pawl can be separatedfrom contact with the buttress 60 after the force is removed. This is inview of the fact that some fall-protection apparatus are occasionallysubjected to “lock-up” testing e.g. in which an operator pulls rapidlyon the safety line 115 to ensure that the braking device properlyengages to arrest the motion. At the end of such a test, the apparatusand braking device thereof should return to their previous,disengaged-and-ready, condition. Thus, a buttress 60 (and othercomponents of the braking device) should be configured to provide thatthe actuation of a flexure-borne pawl is not an irreversible process.Exemplary designs that may facilitate these characteristics are visiblein FIGS. 3 and 4 , and particularly in FIGS. 10-12 .

The value of velocity that causes a flexure-borne pawl 20 to be actuatedcan be set as desired. Such a velocity threshold may be set to anysuitable nominal value, e.g. 6, 8, or 10 feet per second. Such a nominalvalue will correspond to the linear velocity experienced by the extendedportion of safety line 115 (and thus to a user connected thereto). Thiscan be converted to an actual value of rotational velocity of pawl 20 inview of the specific design parameters of the fall-protection apparatus(e.g. the diameter of the drum from which the safety line is unwound,the diameter of the orbit of the pawl, and so on). This can be used toset particular parameters (e.g. the bending stiffness of a flexure arm30, and so on) to ensure that pawl 20 is actuated at a rotationalvelocity that corresponds to the desired threshold of velocityexperienced by the user.

Although in many embodiments a flexure arm may be the only item andmechanism by which the force-displacement relationship of aflexure-borne pawl is established, in other embodiments one or moreadditional methods of biasing may be used as an adjunct to the flexurearm. For example, in some embodiments one or more biasing springs (e.g.coil springs acting in tension) may be present and may be operativelyconnected to a flexure-borne pawl and/or to the flexure arm. In otherembodiments, magnetic biasing may be used as an adjunct to the flexurearm. For example, in some embodiments a magnet may be installed in aside of a pawl-support module, e.g. directly across from a flexure-bornepawl (and separated therefrom by a gap of the type readily visible e.g.in FIG. 7 ). A magnet may be installed in the pawl in addition to, orinstead of, a magnet being present in the pawl-support module. That is,depending e.g. on the metal of which the pawl and/or the pawl-supportmodule is made, in some embodiments only one magnet, interacting with asuitable metal, may be sufficient to achieve the desired effects. Inother embodiments a pair of magnets may be used, acting on each other incombination. Any such magnet(s) may be configured to achieve anattractive force or a repelling force that may act in combination withthe stiffness of the flexure arm to provide a desired force-displacementrelationship.

Acceleration-Actuation

The discussions above have concerned arrangements in which actuation ofa pawl is caused by the velocity of the pawl along its orbital path. Itwill be appreciated that such a pawl may also be subjected toacceleration (e.g. the rate at which drum 80 rotates may rapidlyincrease with time). In some embodiments, any such flexure-borne pawlmay be configured to be relatively insensitive to acceleration. In otherembodiments, depending on the design, the presence of acceleration maye.g. slightly augment the actuation due to velocity, or slightly reduceor retard the actuation due to velocity. In many embodiments, thepawl(s) and flexure arm(s) may be configured so that any such effect ofacceleration is relatively insignificant.

However, in some embodiments, a rotationally-activated braking device ofa fall-protection apparatus may be configured to purposefully rely onacceleration for actuation (and/or for modulation of the response tovelocity) in at least some circumstances. Thus in some embodiments, uponrotation of drum 80, one or more pawls 20, and so on, above apredetermined threshold of acceleration (a), pawl 20 will be urgedbodily away from a disengaged position, radially outward toward and intoan engaged position in which it engages a tooth of the ratchet.

One general approach to providing acceleration-actuation relies onpurposeful control of the relationship of pawl-support plate 40 and drum80. In some embodiments (e.g. that rely largely or completely onvelocity-actuation of pawls) as described previously herein, apawl-support plate 40 and a drum 80 have a fixed relationship so thatplate 40 is not able to rotate relative to drum 80 and vice versa. Forexample, in some embodiments a pawl-support plate 40 may be fixedlyattached to (e.g. bolted to), drum 80. Alternatively, or in addition tothis, both plate 40 and drum 80 may be keyed to common shaft 82 so thatthey cannot rotate relative to each other. In some embodiments apawl-support plate 40 and a drum 80 may sandwich a layer of frictionmaterial 122 therebetween, as shown in FIG. 2 . Such a configurationallows that, in the event that the rotation of plate 40 is stopped upona pawl being actuated, limited rotation of drum 80 relative to plate 40may occur before being stopped by the action of the friction material,as discussed later herein. Such an occurrence still requires a greatdeal of force in order for any relative rotation of plate 40 and drum80.

In contrast, in some embodiments, pawl-support plate 40 and drum 80 maybe configured so that they are relatively easily able to rotate relativeto each other through a predetermined arc of partial rotation of e.g. atmost 90 degrees, 180 degrees, or 270 degrees. That is, they may beconfigured so that they can rotate relative to each other due to anacceleration-derived force arising from a user fall, rather than beingfixed to each other or only being able to rotate relative to each otherupon being exposed to a very high force such as encountered when a pawlis engaged with a ratchet. However, even with this greater ability torotate relative to each other, the vast majority of the time (e.g.during ordinary use in the absence of acceleration due to a fall event),the pawl-support plate will usually remain in a “home” position relativeto the drum, with the drum and the pawl-support plate rotating inlockstep.

One arrangement that can achieve such functioning is depicted in FIG. 8and in partially exploded view in FIG. 9 . These views depict a drum 80,pawl-support plate 40, and pawls 20. Other components are omitted forclarity, but it will be appreciated that such components can be providedin a fall-protection apparatus e.g. of the general type shown in FIGS. 1and 2 , with the items shown in FIGS. 8 and 9 being substituted for thecorresponding items of FIG. 2 . In such embodiments, no layer offriction material is present between drum 80 and pawl-support plate 40.Moreover, if desired, a major sidewall 87 of drum 80, which sidewallcomprises a major surface 83 that may be in at least occasional contactwith a major surface of 42 of pawl-support plate 40, may have a lowcoefficient of friction. In some embodiments, the entirety of drum 80may be made of a material that has a low coefficient of friction. Inother embodiments, sidewall 87 be a separately made item (as evident inFIG. 9 ) that is chosen to have a low coefficient of friction. Forexample, such a sidewall 87 may be made of e.g. poly(oxymethylene),poly(tetrafluoroethylene), and similar organic polymeric materials.Alternatively, the major surface 83 of sidewall 87 (and/or major surface42 of plate 40) may be treated, coated, or otherwise configured to havea low coefficient of friction. Or, a low-friction spacer (e.g. a discmade of poly(oxymethylene) may be present between plate 40 and sidewall87). Any such arrangement or combination thereof can provide that plate40 and drum 80 are able to rotate relative to each other to a sufficientamount to achieve the effects described below.

Camming Bollards

With the necessary freedom of rotation of pawl-support plate 40 and drum80 relative to each other being present, the desiredacceleration-actuation can be provided by using one or more cammingbollards 84 as shown in exemplary embodiment in FIG. 9 . A cammingbollard 84 will be in a fixed position relative to drum 80 (although itmay not necessarily need to be attached or bonded to drum 80; e.g., itmay be sufficient that an end of the bollard is seated in a cavityprovided in drum 80 as shown in FIG. 9 ). Camming bollard 84 protrudesaxially from drum 80 (toward the side of the drum that the pawl-supportplate, pawls, and so on, are present, as is evident in FIG. 9 ). Cammingbollard 84 extends through an elongate slot 43 in pawl-support plate 40(slots 43 are most easily visible in the isolated exploded view of FIG.10 , noting that the camming bollards 84 are omitted from this Figure).This provides that a portion of camming bollard 84 resides within aspace 44 that is radially inward of pawl 20 and/or is radially inward ofa leading segment of flexure arm 30. This arrangement is most easilyseen in FIG. 11 , which is a plan view looking along the axis ofrotation of the drum and pawl-support plate.

Such an arrangement can be configured so that upon acceleration of drum80 (in the direction denoted ω, α in FIG. 11 ) above a predeterminedthreshold value of acceleration a, pawl-support plate 40 will rotatecircumferentially rearwardly (away from plate 40's “home” positionrelative to drum 80), in the direction indicated by arrow 46 in FIG. 11. In other words, due to the freedom of pawl-support plate 40 and drum80 to rotate relative to each other, acceleration of drum 80 will causesupport plate 40 to momentarily “lag” behind drum 80, due to the mass ofthe support plate, pawls, and so on. This will cause each pawl 20 tomove circumferentially rearwardly relative to drum 80 and thus relativeto a camming bollard 84 that is in a fixed position on drum 80. Thismovement of pawl 20 will cause a radially-inward contact surface 27 ofpawl 20 to impinge on camming (contact) surface 85 of camming bollard84. This impingement will have the effect that, as pawl 20 slidablymoves circumferentially rearward relative to camming bollard 84, bollard84 will urge pawl 20 generally radially outward. Pawl 20 will thus bemotivated generally radially outward, toward and e.g. into an engagedposition in which an engaging end of the pawl engages a tooth of theratchet, as can be seen by inspection and comparison of FIGS. 11 and 12. The movement of pawl 20 will be “bodily” movement as described earlierherein.

As evident from FIGS. 11 and 12 , radially-inward contact surface 27 ofpawl 20 may be configured so that impingement of this surface on cammingsurface 85 causes pawl 20 to be urged generally radially outward (insome embodiments pawl 20 may also be urged slightly circumferentiallyrearward, as well). To achieve this, contact surface 27 may be aradially-inwardly-sloping surface. By this is meant that as surface 27is traversed in a leading direction (the direction of rotation w), thesurface is located further and further radially inward, as is evidentfrom FIG. 11 . This, combined with the above-described flexibility offlexure arm 30, provides that as pawl 20 slidably moves along cammingsurface 85 of camming bollard 84, pawl 20 will be urged bodily outward.

To facilitate this functioning, the elongate slot 43 in pawl-supportplate 40, through which camming bollard 84 extends, may exhibit a longaxis that is at least generally locally aligned with the orbital pathfollowed by pawl 20, as is evident from FIGS. 11 and 12 . In someembodiments a camming bollard 84 may be positioned in theabove-mentioned space 44 so that when the drum and pawl-support plateare not rotating (or are rotating very slowly), camming bollard 84 isnot in contact with any portion of pawl 20 or flexure arm 30. In otherembodiments (e.g. as evident in FIG. 11 ), under such a condition,camming bollard 84 may be in contact with a portion of pawl 20 and/orflexure arm 30. Camming bollard 84 thus may, in some embodiments, serveas a physical stop that prevents pawl 20 and/or flexure arm 30 frommoving radially inward.

In some embodiments, the effect of a camming bollard 84 on a pawl 20 maybe achieved purely through physical contact. However, if desired, insome embodiments a camming bollard and/or a pawl 20 may have a magnetinstalled therein. In such embodiments, a magnetic force (e.g. arepelling force) may provide at least some of the force by which thecamming bollard acts to urge the pawl radially outward.

In at least some embodiments the one or more camming bollards 84 may bepart of a load-bearing (force-transmitting) path between drum 80 andpawl-support plate 40. Thus, camming bollards 84 may be made of anysuitable material, e.g. steel. In some embodiments the far end of eachbollard (e.g., the far right end of bollards 84 as shown in FIG. 9 ) maybe seated in a receptacle of drum 80, which receptacle may be reinforcedto enhance the load-bearing and load-transmitting properties of theinterface between the drum and the camming bollard. One such receptacleis visible, unnumbered, in the drum of FIG. 9 . Of course, in someembodiments bollards 84 may serve purely for the purposes of camming asdescribed earlier herein; if so, some other posts or similar featuresmay be provided that serve as part of a load-bearing path between plate40 and drum 80. Drum 80 may be made of any material that exhibitsproperties commensurate with the desired strength. In variousembodiments, drum 80 may be made of a molded polymer such as e.g.glass-fiber-reinforced nylon; or, drum 80 may be made of a metal such ase.g. cast aluminum. Similarly, pawl-support plate 40 may be made of anymaterial with suitable properties, e.g. steel.

In some embodiments the camming bollards may serve as physical stopsthat limit the rotation of drum 80 relative to pawl-support plate 40.That is, in some embodiments the rotation of drum 80 relative to plate40 may be limited by the distance that camming bollard 84 can travelwithin the elongate length of slots 43 of plate 40, as is evident frominspection of FIGS. 11 and 12 . That is, in some embodiments, the lengthof an elongate slot 43 of pawl-support plate 40, in combination with thepresence of a bollard 84 that extends therethrough, can define thelimits of the arc of rotation of pawl-support plate 40 relative to drum80. In various embodiments, the length of an elongate slot 43 can be setso that this arc of rotation is at least 5, 10, 15, 20, or 25 degrees.In further embodiments, the length of elongate slot 43 can be set sothat this arc of rotation is at most 80, 70, 60, 50 or 40 degrees. (Theparticular slots 43 depicted e.g. in FIG. 12 appear to establish an arcof rotation of approximately 35 degrees.)

The above disclosures illustrate how a single type of pawl may beconfigured so that it can be actuated by absolute velocity, and/or canbe actuated by acceleration. In some embodiments, the actuation of aflexure-borne pawl 20 by acceleration, and by velocity, may be at leastgenerally independent of each other. In other words, in some embodimentsa pawl 20 may be actuated upon the rotational velocity of the pawlexceeding a certain threshold value, substantially regardless of theacceleration that exists when that threshold value of velocity isreached, and substantially regardless of the particular accelerationhistory that was experienced by the pawl in reaching that thresholdvalue of velocity. Similarly, a pawl 20 may be actuated upon theacceleration of the pawl exceeding a certain threshold value,substantially regardless of the absolute value of the velocity thatexists when that threshold value of acceleration is reached, andsubstantially regardless of what velocity may or may not have beenexperienced by the pawl prior to reaching that threshold value ofacceleration. (By substantially regardless is meant that a parametercontributes less than 10% to the effect in question.) In suchembodiments, the predetermined threshold values of velocity andacceleration may be set substantially independently of each other. Thiswill have advantages that are readily appreciated by ordinary artisans.In some embodiments it may be advantageous that the acceleration servesto modulate the response to velocity, e.g. to lower the threshold valueof velocity-actuation. This may be achieved for example if the movementof a flexure arm along a bollard with which the flexure arm is incontact, serves to change the velocity-response of the flexure arm, e.g.by changing the effective undamped length of the flexure arm.

The above explanations have been couched in terms of a pawl beingresponsive to “acceleration”. In this regard it is noted that, strictlyspeaking, a body (e.g. a pawl 20) that is following an orbital path iscontinuously experiencing acceleration due to the change in thedirection of motion. (In other words, velocity is a vector quantity, andany change in the magnitude or direction of the velocity, corresponds toacceleration.) Those of ordinary skill will appreciate that the term“acceleration” as used herein (e.g. with regard to anacceleration-actuated pawl) specifically denotes so-called tangentialacceleration of a body that is following an orbital path. (Suchtangential acceleration will be generally aligned with block arrow 29 asshown in FIG. 12 .) In other words, the acceleration that causesactuation of a pawl 20 corresponds to a change in the magnitude of thevelocity of a body along its orbital path. Acceleration that resultsmerely from the body following an orbital path at constant velocity(i.e., centripetal acceleration) has little or no effect; the velocityof the body along this orbital path must change in order foracceleration-actuation of the type disclosed herein to occur.

The value of acceleration that causes a pawl 20 to be actuated can beset as desired. Such an acceleration threshold may be set to anysuitable nominal value, e.g. 0.6 to 0.8 g. This is a nominal value thatcorresponds to the linear acceleration experienced by the extendedportion of safety line 115 (and thus to a user connected thereto). Thiscan be converted to an actual value of acceleration of pawl 20 in viewof the specific design parameters of the fall-protection apparatus (e.g.the diameter of the drum from which the safety line is unwound, thediameter of the orbit of the pawl, and so on). This can be used to setparticular parameters that ensure that pawl 20 is actuated at arotational acceleration (specifically, a tangential acceleration) thatcorresponds to the desired threshold of acceleration experienced by theuser.

Further details of the particular arrangements depicted in FIGS. 8-10will now be described. As noted, in some embodiments a drum 80 maycomprise a main section that includes one major sidewall, with anothermajor sidewall 87 being a separately-made item that is then combinedwith the main section to provide drum 80 (and to establish a space 88between the sidewalls, that accepts the wound-up length of safety line115). As shown in FIG. 10 , pawl-support plate 40 can comprisebuttresses 60 that function in a similar manner as described earlierherein. Pawl-support module 51, including flexure arm anchors 50 andflexure arms 30, can be attached to plate 40 e.g. by fasteners 45. (Inthe depicted embodiment, pawl-support module 51 and flexure arms 30 areintegral; however, pawls 20 are separately made and are attached to theleading ends of flexure arms 30.) Various aspects of the pawls, flexurearms, and so on (e.g. the amount of circumferential wrap and so on) ofthis design have already been discussed herein.

It will be appreciated that the arrangements disclosed herein can allowa flexure arm 30 to be configured (e.g. to have the desiredflexibility/stiffness) to allow a pawl 20 to be actuated by apredetermined velocity, and/or by a predetermined acceleration. Inparticular, the providing of a buttress 60 to substantially free theflexure arm from having to bear a high load upon the pawl being engagedwith a ratchet tooth, can enable the freedom to design the flexure armto achieve both of these goals.

As mentioned earlier herein, some fall-protection apparatus areoccasionally subjected to “lock-up” testing e.g. in which an operatorpulls rapidly on the safety line 115 to ensure that the braking deviceproperly engages to arrest the motion. At the end of such a test, theapparatus and braking device thereof should be able to return to theirprevious, disengaged-and-ready condition. In some embodiments adedicated biasing mechanism may be provided that urges pawl-supportplate 40 circumferentially forward (i.e., in a leading direction)relative to drum 80, so that plate 40 can be returned to its home/readyposition at the conclusion of a lock-up test. However, in someembodiments it may not be necessary to provide plate with a dedicatedbiasing mechanism. Rather, it has been found that in some embodiments abiasing member 86 (e.g. a torsion spring as discussed previously) thatserves to bias drum 80 toward rotating in a direction that will retractsafety line 115 onto the drum, may serve this purpose. Such biasingmembers are conventionally configured to retract line 115 (and thus toremove any slack in line 115) if the user moves toward the apparatus.However, if pawl-support plate 40 and drum 80 are configured to exhibitfreedom of relative rotation in the general manner described above, thisbiasing of drum 80 may be sufficient to serve the purpose of restoringpawl-support plate 40 to its home position after a lock-up test. Thus inat least some embodiments, such a biasing member of drum 80 may perform“double-duty” and eliminate any need to provide a dedicated biasingmechanism for pawl-support plate 40. However, in some embodiments adedicated biasing mechanism may be provided for pawl-support plate 40,e.g. to bias plate 40 relative to drum 80. Various mechanisms andarrangements by which a pawl-support plate may be biased relative to adrum are described in detail in U.S. Provisional Patent Application No.62/705,535, filed 2 Jul. 2020, entitled Fall-Protection ApparatusComprising Braking Device With Velocity-Actuated, Acceleration-ModulatedPawl(s), which is incorporated by reference herein in its entirety.

The above discussions have described the use of acceleration-actuatedpawls as an adjunct to a braking system that relies on velocity-actuatedpawls that are flexure-borne pawls. However, it is noted that theconcept of an acceleration-actuated pawl as achieved e.g. by a cammingsystem as disclosed herein, is independent of any requirement that thepawl must be flexure-borne. Rather, based on the disclosures herein, anordinary artisan will appreciate that a system of camming bollards orlike mechanisms, could be applied to pivot-mounted pawls of the generaltype described earlier here. Such pawls can thus pivot into an engagedposition upon exceeding a predetermined threshold of velocity; and/or,such pawls could be motivated to pivot into an engaged position by wayof the pawl impinging onto a camming bollard of the general typedescribed above, as the result of sufficient acceleration.

In general, in some embodiments (regardless of the particular type ofpawl) a camming system as described above may be used to provide anacceleration-actuated braking system. That is, in some embodiments thepawls and associated components may be configured so that they are farmore likely to be actuated by acceleration than by absolute velocity.Thus, an acceleration-actuated braking device that relies on a cammingsystem as described herein may be used without regard to whether thebraking device is able to be velocity-actuated. Such arrangements anduses are within the scope of the disclosures herein.

As noted, the arrangements herein cause at least one pawl to engage witha tooth 91 of a ratchet 90 as indicated in exemplary embodiment in FIG.7 . This can either stop the rotation of drum 80 directly (e.g. in thecase of a “hard-stop” arrangement as mentioned earlier herein), or canactivate a friction brake that brings the rotation of drum 80 to a halt.It will be appreciated that numerous variations of ratchets, and themanner in which one or more pawls engage with a tooth of the ratchet,are possible. Typically, any such pawl will be configured so that theengaging end 22 of a pawl 20 (in fact, the entirety of the pawl 20) willtravel from a disengaged position to an engaged position by movinggenerally radially outward. Such arrangements are typically used with aradially-inward-facing ratchet (meaning a ratchet, e.g. a ratchet ringor partial ring, with radially inward-facing teeth).

In some embodiments a ratchet, rather than being provided e.g. as atoothed ring that is made separately and inserted into a housing of afall-protection apparatus, may be provided e.g. as an integral (e.g.molded, cast, or machined) feature of the housing of the apparatus. ThePROTECTA fall-protection apparatus, available from 3M Fall Protection,Red Wing, Minn., and discussed in more detail below, is an example of aproduct that uses this type of ratchet. Another possible variation inratchet design is presented in U.S. Pat. No. 9,488,235, in which aratchet takes the form of a single tooth (“stop member”) that isprovided as an integral part of a bracket (e.g., a load-bearing bracket)of a fall-protection apparatus. (The PROTECTA product, and the apparatusdescribed in the '235 patent, rely on a completely different arrangementof pawls than disclosed herein; these items are cited merely toillustrate potential variations in ratchets.) In fact, the ratchet 90depicted in FIGS. 11 and 12 herein is another example of a ratchet thatcomprises only a single tooth 91, as is clear from FIGS. 11 and 12 .

From the above discussions it will be clear that a ratchet of arotationally-activated braking device can be any component (e.g. atoothed ring, a partial ring, or a portion of a fall-protection bracketor housing, and so on) that presents at least one tooth that can beengaged by an engaging end of a pawl to initiate a braking operation ofthe rotationally-activated braking device. It is emphasized that theterm “ratchet” is used for convenience of description; use of this termdoes not require that the ratchet and pawl(s) must necessarily bearranged e.g. so that relative rotation of these components is permittedin one direction but is precluded in the opposite direction. (However,the ratchet and pawl(s) can be arranged so that such functionality isprovided if desired.)

In some embodiments a rotationally-activated braking device as disclosedherein can bring a drum to a “hard stop” (e.g. the braking device mayrely on a ratchet that is non-rotatably fixed to the housing of theapparatus), as discussed earlier herein. However, in other embodiments arotationally-activated braking device as disclosed herein will comprise(e.g. will work in concert with) a friction brake. In general, afriction brake will comprise at least one layer of friction material andat least one rotatable member, with a friction-braking surface of thelayer of friction material being in contact (typically, at all timesduring ordinary use of the fall-protection apparatus) with a contactsurface of the rotatable member. By a rotatable member is meant an item(e.g., a disk, ring, rotor, or the like) that is configured so that themember and the layer of friction material can be set into rotatingmotion relative to each other upon sufficient differential torque beingapplied to the layer of friction material and the rotatable member asthe result of the engaging of a pawl with a ratchet of therotationally-activated braking device. In many embodiments, thefriction-braking surface of the layer of friction-braking material andthe contact surface of the rotatable member are constantly pressedtogether to provide sufficient static frictional force that, as a humanuser moves about a workplace in ordinary use of the apparatus, there isno relative motion between the two surfaces. However, upon the engagingof a pawl with a ratchet of the rotationally-activated braking device,sufficient differential torque is generated to overcome the staticfrictional force, such that relative motion of the two surfaces (andhence relative motion of the rotatable member and the layer of frictionmaterial) may occur. The rotatable member and the layer of frictionmaterial are configured so that this relative rotation of the layer offriction material and the rotatable member will be slowed and/or broughtto a halt by the frictional forces between the friction-braking surfaceof the layer of friction material and the contact surface of therotatable member. The slowing of this relative rotation will serve toslow (e.g. halt) the rotation of a drum bearing a safety line.

The above is a general description of a friction brake and its function;many variations are possible. In some embodiments, it may be convenientfor a ratchet of the rotationally-activated braking device to serve as arotatable member of the friction brake of the braking device. In manysuch designs, the ratchet is able to rotate with respect to the housingof the apparatus, but typically remains stationary during ordinary useof the apparatus. That is, the drum may rotate (relatively slowly)relative to the housing to extend and retract the safety line as a humanuser moves about a workplace. However, the ratchet, not being subjectedto any rotational force, and being frictionally constrained by one ormore layers of friction material, does not rotate relative to thehousing. In the event that the drum begins to rotate rapidly e.g. due toa fall, the engaging end of a pawl engages with a tooth of the ratchetand overcomes this frictional constraint and causes the ratchet torotate relative to the layer(s) of friction material and thus relativeto the housing of the apparatus. The friction between thefriction-braking surface of the friction material and the contactsurface of the ratchet then slows or halts the rotation of the ratchetrelative to the housing of the apparatus thus slowing or halting therotating of the rotatable drum relative to the housing of the apparatus.The assembly shown in exploded view in FIG. 13 is one example of thisgeneral type of friction brake. Such an assembly may rely on a ratchet90 that, along with a layer of friction material 122, is sandwichedbetween a pressurization ring 125 and a backing plate 126. Ring 125 andplate 126 may be pressed together (e.g. by way of bolts that passthrough the various orifices visible in FIG. 13 ) with a desired forcethat imparts the desired frictional characteristics. It will beappreciated that the items of FIG. 13 are merely one way of achievingsuch functionality; various modifications are possible (for example,rather than pressurization ring 125 and/or backing plate 126 being aseparately-made item that is installed into a housing of afall-protection apparatus, a portion of the housing itself may servesuch a role). Many arrangements of friction brakes are possible. Forexample, in some embodiments a ratchet may comprise two contact surfacesand may be sandwiched between two layers of friction material. In otherembodiments, a ratchet of a friction brake may only comprise a singlecontact surface which may be in contact with only a single layer offriction material.

In some embodiments, the rotatable member of a friction brake of arotationally-activated braking device may not necessarily be a ratchetof the braking device. Rather, in some cases the ratchet of therotationally-activated braking device and the rotatable member of thefriction brake of the rotationally-activated braking device may beseparate items. In one exemplary arrangement of this general type, apawl-support plate 40 may serve as a rotatable member of the frictionbrake. For example, a layer of friction material 122 may be arranged inbetween the pawl-support plate 40 and drum 80, with a first majorfrictional surface 123 of friction material 122 in contact with acontact surface 42 of plate 40 as indicated in FIGS. 2 and 3 herein. Asecond major frictional surface 124 of friction material 122 maysimilarly be in contact with a contact surface of drum 80. The entireassembly can be pressed together to impart the desired frictionalcharacteristics between these surfaces. (It will be appreciated thatsuch an arrangement would not likely be used in embodiments in whichdrum 80 and pawl-support plate 40 are desired to have freedom ofrelative rotation, e.g. in the event that camming-derivedacceleration-actuation is desired.) With such an arrangement, theengaging of an engaging end of a pawl with a tooth of the ratchet willcause the pawl-support plate 40 on which the pawl is mounted tonear-instantaneously cease rotating, while drum 80 may continue torotate momentarily. The frictional force between the contact surface ofrotatable member (pawl-support plate) 40 and the first friction-brakingsurface of the layer of friction material 122, and/or between thecontact surface of the drum and the second friction-braking surface ofthe layer of friction material, will slow or halt the rotation of thedrum. Often, the drum may be brought to a halt before the drum hascompleted, for example, one full revolution. (In some embodiments ofthis general type, the layer of friction material may be e.g. fixedlyattached to the drum or to the pawl plate, so that the frictionalinteraction only occurs at one interface rather than at two interfaces.)The arrangement shown in FIG. 2 herein is an example of this generalapproach. Various products available from 3M Fall Protection, Red Wing,Minn., under the trade designation PROTECTA provide further examples offall-protection products of this general type.

It will be appreciated that many variations of the above-presentedexemplary arrangements may be employed. For example, a separate plate,e.g. attached to the drum or co-mounted on a common shaft so that theseparate plate is not rotatable relative to the drum, may provide acontact surface for a layer of friction material, rather than having thefriction material directly in contact with a wall of the drum. In someembodiments a layer of friction material may itself be disposed on (e.g.laminated or bonded to) a support plate as discussed herein. In otherembodiments, a layer of friction material may be “free-standing” ratherthan being bonded to a support plate. Any suitable friction material maybe used, e.g. cork, rubber, and so on. Friction materials that may beparticularly useful are described in U.S. patent application Ser. No.16/630,584 and in corresponding PCT Published Application WO2019/012454,both of which are incorporated by reference herein in their entirety.The above discussions make it clear that any compatible type, design orarrangement of ratchet, friction material, and so on, may be used incombination with the herein-disclosed arrangement of pawls.

The arrangements disclosed herein may be advantageously used in anyfall-protection apparatus; in particular, in a self-retracting lifeline.In addition to the documents previously cited herein, fall-protectionapparatus such as e.g. self-retracting lifelines in which thearrangements disclosed herein may be advantageously utilized, aredescribed in U.S. Pat. Nos. 8,181,744, 8,256,574, 8,430,206, 8,430,207,8,511,434, and 9,488,235, and in U.S. Published Patent Application2016/0096048.

In some embodiments the fall-protection apparatus is a self-retractinglifeline which meets the requirements of ANSI Z359.14-2014. In general,the arrangements disclosed herein may be used in any fall-protectionapparatus in which there is a desire to enhance the performance of theproduct, e.g. by minimizing the occurrence of nuisance lockups that mayoccur during movements about the workplace, while ensuring that thebraking device responds as quickly as possible in the event of an actualfall.

A fall-protection apparatus as described herein may comprise a housing,drum, rotationally-activated braking device, etc., of any desired size.In some embodiments, the apparatus may be sized so that it can serve asa so-called “personal” self-retracting lifeline as discussed laterherein. The size of the rotationally-activated braking device may becharacterized e.g. in terms of the diameter of the orbital pathway 25that is followed by pawl(s) 20. In various embodiments, the diameter oforbital path 25 may be at least 20, 30, 40, or 50 mm; in furtherembodiments, the diameter of orbital path 25 may be at most 150, 120,90, or 60 mm.

In various embodiments, a fall-protection apparatus as described hereinmay be used in concert with, or as part of, any suitable fall-protectionsystem such as e.g. a horizontal lifeline or retractable horizontallifeline, a positioning lanyard, a shock-absorbing lanyard, a ropeadjuster or rope grab, a vertical safety system (such as e.g. a flexiblecable, rigid rail, climb assist, or fixed ladder safety system), aconfined-space rescue system or hoist system, and so on. In someembodiments a fall-protection apparatus as disclosed herein may comprisea housing configured so that the interior of the apparatus is at leastpartially sealed (such as in the product line available from 3M FallProtection under the trade designation (SEALED-BLOK) e.g. for use inharsh or marine environments. In some cases a fall-protection apparatusas disclosed herein may be suited for use in so-called “leading edge”workplace environments. It is still further noted that the discussionsherein have primarily concerned apparatus (e.g. self-retractinglifelines) that comprise a housing that is e.g. mounted to an overheadanchorage and that comprises a safety line with a distal end that can beattached to a harness of a human user. It will be understood that thearrangements disclosed herein may also be used in e.g. “personal”self-retracting lifelines that comprise a housing that is mountable to aharness of a human user and that comprises a safety line with a distalend that can be attached e.g. to an overhead anchorage. Such apparatusare exemplified by the product line available from 3M Fall Protectionunder the trade designations TALON and NANO.

It will be understood that any such fall-protection apparatus mayinclude, or be used with, various ancillary items which are notdescribed in detail herein. Such items may include, but are not limitedto, one or more of lanyards, shock absorbers, tear strips, harnesses,belts, straps, paddings, tool holsters or pouches, impact indicators,carabiners, D-rings, anchorage connectors, and the like. Many suchapparatus, products, and components are described in detail e.g. in the3M DBI-SALA Full-Line Catalog (Fall 2016). Although in many embodimentsit may not be necessary due to the presence of the friction brake, insome embodiments the safety line of the apparatus may comprise anin-line shock absorber e.g. of the type described earlier herein. (Anexemplary shock absorber is depicted in FIG. 1 of thepreviously-mentioned U.S. Pat. No. 9,488,235 patent, which isincorporated by reference in its entirety herein.) In other embodiments,no such shock absorber will be present. It will be understood that afall-protection apparatus that is “non-motorized” as defined anddescribed earlier herein, may still include such items as one or moreelectrically-powered sensors, monitors, communication units, actuators,and the like. Although discussions previously herein have primarilyconcerned products that completely arrest (stop) the motion of a humanuser, it is stipulated that in some embodiments, a fall-protectionapparatus as described herein may serve merely to slow the fall of auser, and/or to allow the user to descend at a controlled rate.

It will be apparent to those skilled in the art that the specificexemplary elements, structures, features, details, configurations, etc.,that are disclosed herein can be modified and/or combined in numerousembodiments. All such variations and combinations are contemplated bythe inventor as being within the bounds of the conceived invention, notmerely those representative designs that were chosen to serve asexemplary illustrations. Thus, the scope of the present invention shouldnot be limited to the specific illustrative structures described herein,but rather extends at least to the structures described by the languageof the claims, and the equivalents of those structures. Any of theelements that are positively recited in this specification asalternatives may be explicitly included in the claims or excluded fromthe claims, in any combination as desired. Any of the elements orcombinations of elements that are recited in this specification inopen-ended language (e.g., comprise and derivatives thereof), areconsidered to additionally be recited in closed-ended language (e.g.,consist and derivatives thereof) and in partially closed-ended language(e.g., consist essentially, and derivatives thereof). Although varioustheories and possible mechanisms may have been discussed herein, in noevent will such discussions serve to limit the claimable subject matter.To the extent that there is any conflict or discrepancy between thisspecification as written and the disclosure in any document that isincorporated by reference herein but to which no priority is claimed,this specification as written will control.

What is claimed is:
 1. A fall-protection apparatus comprising: a drumwith a safety line connected thereto and that is rotatable relative to ahousing of the apparatus; and, a rotationally-activated braking devicethat comprises at least one pawl and at least one ratchet with at leastone tooth that is engagable by an engaging end of the at least one pawl,wherein the pawl is a flexure-borne pawl that is attached to a flexurearm.
 2. The apparatus of claim 1 wherein the apparatus is configured sothat when the drum is not rotating, the at least one pawl is in adisengaged position; and, so that upon rotation of the drum above apredetermined threshold value of rotational velocity, the pawl is urgedby centrifugal force, bodily generally radially outward into an engagedposition in which an engaging end of the flexure-borne pawl engages atooth of the ratchet.
 3. The apparatus of claim 1 wherein a trailing endof the pawl is attached to a leading end of the flexure arm and whereina leading end of the pawl is the engaging end that is configured toengage a tooth of the ratchet.
 4. The apparatus of claim 1 wherein atrailing end of the flexure arm is attached to a flexure arm anchor thatprotrudes axially from a pawl-support plate that is axially co-mountedwith, and is co-rotatable with, the drum.
 5. The apparatus of claim 1wherein the flexure arm is elongate with an elongate length andcomprises a thinnest dimension that is oriented within plus or minusdegrees of a radially-inward-outward direction of the drum andpawl-support plate, along at least 80% of the elongate length of theflexure arm.
 6. The apparatus of claim 1 wherein the flexure arm andpawl collectively exhibit an at least 70 degree circumferential wrap,measured from a flexure arm anchor to which the trailing end of theflexure arm is attached, to the leading end of the pawl.
 7. Theapparatus of claim 1 wherein a long axis of the flexure arm exhibits alocal alignment angle with respect to an orbital path of the pawl, thatis less than plus or minus 30 degrees, along at least 90% of the entirelength of the flexure arm.
 8. The apparatus of claim 1 wherein therotationally-activated braking device comprises multiplecircumferentially-spaced flexure-borne pawls, each pawl being attachedto the end of a separate flexure arm that extends from a separateflexure arm anchor.
 9. The apparatus of claim 8 wherein the multipleflexure arm anchors are each an integral component of a single, integralpawl-support module that protrudes axially from the pawl-support plate,and wherein the multiple flexure arm anchors are circumferentiallyspaced along a perimeter of the single, integral pawl-support module.10. The apparatus of claim 9 wherein the multiplecircumferentially-spaced flexure-borne pawls, the multiple flexure arms,and the single, integral pawl-support structure that comprises themultiple flexure arm anchors, are all integral components of a single,integral, injection-molded metal structure that is attached to thepawl-support plate.
 11. The apparatus of claim 1 wherein thepawl-support plate comprises a buttress that protrudes axially from apawl-support plate that is axially co-mounted with and is co-rotatablewith the drum and to which a trailing end of the flexure arm isconnected; and, wherein at least a portion of the buttress is positionedcircumferentially rearward of at least a portion of the trailing end ofthe pawl.
 12. The apparatus of claim 11 wherein the apparatus isconfigured so that when the pawl is in a disengaged position, no portionof the pawl is in contact with the buttress; and, wherein the apparatusis further configured so that when the leading end of the pawl engages atooth of the ratchet upon rotation of the drum above a predeterminedrotational velocity, the pawl is urged circumferentially rearwardrelative to the pawl-support plate causing at least a portion of thetrailing end of the pawl to contact the buttress so that the buttressbears at least a portion of a force that is applied to the pawl upon theengaging of the pawl with the tooth of the ratchet.
 13. The apparatus ofclaim 12 wherein the buttress bears at least 80% of the force that isapplied to the pawl upon the engaging of the pawl with the tooth of theratchet.
 14. The apparatus of claim 1 wherein the rotationally-activatedbraking device comprises multiple circumferentially-spaced,flexure-borne pawls, each pawl being attached to the end of a separateflexure arm that extends from a separate flexure arm anchor; and,wherein the device comprises multiple circumferentially-spacedbuttresses, each buttress being positioned circumferentially rearward ofat least a portion of a trailing end of a pawl.
 15. The apparatus ofclaim 1 wherein the apparatus comprises a pawl-support plate that isrotatable relative to the drum through an arc of partial rotation andthat comprises a flexure arm anchor that protrudes axially from thepawl-support plate and to which the flexure arm is attached, and whereinthe drum comprises at least one camming bollard that is fixed to thedrum and protrudes axially from the drum so as to extend through anelongate slot in the pawl-support plate so that a portion of the cammingbollard resides within a space radially inward of the pawl and/orradially inward of a leading segment of the flexure arm.
 16. Theapparatus of claim 15 wherein the apparatus is configured so that uponacceleration of the drum above a predetermined threshold value ofacceleration, the pawl-support plate will rotate circumferentiallyrearwardly relative to the drum, causing the pawl to movecircumferentially rearwardly relative to the drum and to the cammingbollard, so that a radially-inward contact surface of the pawl and/or ofthe leading segment of the flexure arm impinges on a camming surface ofthe camming bollard causing the pawl to be urged bodily generallyradially outward toward an engaged position in which an engaging end ofthe pawl engages a tooth of the ratchet.
 17. The apparatus of claim 15wherein the pawl comprises a radially-inward major surface that is acontact surface that is configured to impinge on the camming surface ofthe camming bollard and to slidably move along the camming surface ofthe camming bollard in a generally circumferentially rearward direction;and, wherein the contact surface of the pawl is aradially-inward-sloping surface.
 18. The apparatus of claim 15 whereinthe camming bollard is a load-bearing item that forms a part of aforce-transmissive pathway between the drum and the pawl-support plate.19. The apparatus of claim 15 wherein the elongate slot in thepawl-support plate through which the camming bollard extends, exhibits along axis that is at least generally locally aligned with an orbitalpath of the pawl, and wherein an elongate length of the elongate slot inthe pawl-support plate defines the arc of partial rotation through whichthe pawl-support plate is rotatable relative to the drum.
 20. Theapparatus of claim 1 wherein the apparatus is configured so that uponengaging of the engaging end of the pawl with a tooth of the ratchet,the drum is brought to a hard stop and wherein the safety line that isattached to the drum includes an in-line shock-absorber.
 21. Theapparatus of claim 1 wherein the rotationally-activated braking devicecomprises a friction brake comprising a layer of friction material and arotatable member with a contact surface that is in contact with afriction-braking surface of the layer of friction material, and whereinthe braking device is configured so that upon engaging of the engagingend of the pawl with a tooth of the ratchet, the drum continues torotate relative to the pawl-support plate until brought to a halt by thefriction brake.
 22. The apparatus of claim 1 wherein therotationally-activated braking device comprises a friction brakecomprising a layer of friction material that is in contact with asurface of the ratchet, and wherein the braking device is configured sothat upon engaging of the engaging end of the pawl with a tooth of theratchet, the ratchet begins to rotate and continues to rotate untilbrought to a halt by the friction brake.
 23. The apparatus of claim 1wherein the apparatus is a self-retracting lifeline in which the safetyline comprises a proximal end that is connected to the rotatable drumand a distal end that is attachable to a harness of a human user of theapparatus or to an anchorage of a workplace, and in which the rotatabledrum is biased toward rotating in a direction that will retract thesafety line onto the drum.